Cambridge A Level Physical Science 8780 — 2017 Oct/Nov Paper 2 · Variant 1

1 In liquids and gases, molecules are in constant motion. Describe, in terms of the kinetic model, two differences between liquids and gases. .......................................................................................................................................................... ......................................................................................................................................................[2]

Mark scheme: 1 any two from: in a gas there are negligible forces between molecules, in a liquid significant forces in a gas molecules are spaced well apart, in a liquid close together in a gas molecules are free to move, in a liquid they are constrained by other molecules 2

2 Ethene can react as shown in the equation. H H H H n C C C C H H H H n (a) Give the name of this type of reaction. ...............................................................................................................................................[1] (b) State why the safe disposal of the type of product formed in this reaction is difficult. ................................................................................................................................................... ...............................................................................................................................................[1]

Mark scheme: 2(a) (addition) polymerisation 1 2(b) (the product is) non-biodegradable / produces harmful combustion products 1

3 Fig. 3.1 shows an object that has only two forces acting on it. The forces have equal magnitudes F and act in opposite directions. F F object Fig. 3.1 State what is meant by equilibrium and explain why this object is not in equilibrium. .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[2]

Mark scheme: 3 resultant force AND resultant torque = 0 1 forces are not aligned / there is a torque on the object 1

4 Radioactive decay is both random and spontaneous. State what is meant by the decay being random, .......................................................................................................................................................... .......................................................................................................................................................... spontaneous. .......................................................................................................................................................... .......................................................................................................................................................... [2]

Mark scheme: 4 cannot predict when a particular nucleus will decay 1 decay not affected by external conditions 1

5 Nitrogen monoxide and carbon monoxide are both formed in internal combustion engines. These pollutants are removed from the exhaust gases using a catalyst. (a) State what is meant by the term catalyst. ................................................................................................................................................... ...............................................................................................................................................[1] (b) Name a suitable catalyst for removing nitrogen monoxide and carbon monoxide from exhaust gases. ...............................................................................................................................................[1] (c) Write an equation to show how nitrogen monoxide and carbon monoxide react together in the presence of a catalyst. ...............................................................................................................................................[1]

Mark scheme: 5(a) a substance that increases the rate of a reaction without being consumed itself or used up OR increases rate and provides an alternate reaction pathway with a lower activation energy 1 5(b) platinum / rhodium / palladium 1 5(c) 2NO + 2CO → N2 + 2CO2 1

6 Fig. 6.1 shows two parallel metal plates with a potential difference (p.d.) of 5000 V across them. metal plate +5000 V d 0 V metal plate Fig. 6.1 (not to scale) (a) On Fig. 6.1, draw at least five lines of force to show the electric field between the plates. [2] (b) The distance d between the plates is 2.0 cm. Calculate the electric field strength between the plates. electric field strength = .................................................N C−1 [2]

Mark scheme: 6(a) minimum of 5 straight vertical lines between the plates, starting and finishing on a plate and none touch / cross AND distributed evenly across full width of plate 1 arrows on all given lines pointing downwards 1 6(b) 5000 ÷ (2.0 × 10–2) 1 250 000 (NC–1) 1

7 Mirabilite is a mineral. It is hydrated sodium sulfate, Na2SO4.xH2O, where x is the number of molecules of water of crystallisation. Mirabilite contains 55.9% by mass of water. Calculate x. x = ...........................................................[3]

Mark scheme: 7 Mr(Na2SO4) = 142.1 AND Mr(H2O) = 18 1 percentage of Na2SO4 = 100 – 55.9 = 44.1% AND Na2SO4 H2O 44.1 142.1 55.9 18 0.310 3.11 1 10 1 x = 10 1

8 Explain why the atomic radius decreases across Period 3 of the Periodic Table, from Na to Cl. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[3]

Mark scheme: 8 increase in the number of protons (across the period) 1 same number of shells / same amount of shielding or screening 1 stronger attraction between nucleus AND electrons 1

9 Diffraction of visible light occurs when the light passes through a gap. Suggest a suitable gap width to observe diffraction of visible light and give a reason for your answer. gap width ........................................................................................................................................... reason ............................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... [2]

Mark scheme: 9 1 gap must be a similar size to the wavelength 1

10 There are four isomeric alcohols with molecular formula C4H10O. (a) When heated under reflux conditions with acidified potassium dichromate(VI), isomer A did not react. Draw the structural formula for isomer A in the box. isomer A C4H10O [1] (b) When heated separately under reflux conditions with acidified potassium dichromate(VI), two of the other isomers reacted to form compounds X and Y. Compounds X and Y contain the same functional group and have the same molecular formula, C4H8O2. Draw the structural formulae for compound X and for compound Y in the boxes. compound X compound Y C4H8O2 C4H8O2 [2] (c) When heated under reflux conditions with acidified potassium dichromate(VI), the fourth isomer reacted to form compound Z with molecular formula C4H8O. Draw the structural formula for compound Z in the box. compound Z C4H8O [1]

Mark scheme: 10(a) isomer A C4H10O = (CH3)3COH 1 10(b) Compound X C4H8O2 = CH3CH2CH2CO2H 1 Compound Y C4H8O2 = (CH3)2CHCO2H 1 10(c) Compound Z C4H10O = CH3CH2COCH3 1

11 An electric heater is rated at 2.4 kW, 230 V. The heater is connected to a 230 V mains supply. (a) Calculate the resistance of the heater. resistance = ......................................................Ω [1] (b) The supply voltage drops to 210 V. Calculate the drop in power output from the heater. Assume that the resistance of the heater does not change. drop in power = ..................................................... W [2]

Mark scheme: 11(a) 22.0 1 11(b) 2102 ÷ 22.0 / 2000 (kW) 1 400 (W) 1